In many industrial and commercial distribution environments, there is a need to determine information about a particular item or package quickly, and with a minimum of user intervention. For example, in a manufacturing environment, parts must be tracked at all times from the assembly stage until the delivery of the particular part to the customer. The technology to perform these tracking functions has evolved from labor-intensive manual processes, to optical scanning, involving barcode readers that scan universal product code (UPC) labels, and into the radio frequency identification (RFID) domain.
In an optical scanning system, a barcode reader generates a low-power laser signal that is reflected off a paper label that includes a UPC. The reflected signal is converted to digital information that can be interpreted by a computer. However, in an optical scanning system, the optics through which the low-power laser signal and its reflection are passed can become dirty and require frequent maintenance. Further, the UPC label can only be read when the barcode is visible to the barcode reader, thus requiring the label to be affixed to an outer surface of the package. These factors increase the cost of optical barcode scanning systems, and limit their acceptance in industrial and commercial environments.
In an RFID system, a passive responder receives energy generated by an interrogator unit. The responder generates a message in response to the presence of the energy received from the interrogator unit. However, these systems can require complex circuitry to be embedded in the passive responder, thereby increasing cost and, in turn, limiting the acceptance of RFID systems.